Tab Audio Capture: Browser-side connect/disconnect functionality.

content/browser/renderer_host/media/audio_renderer_host.h

Index: content/browser/renderer_host/media/audio_renderer_host.h
diff --git a/content/browser/renderer_host/media/audio_renderer_host.h b/content/browser/renderer_host/media/audio_renderer_host.h
index 43e9395ac50ff90293b55f24cda1c8a1e59c78cf..5853f9d2457474554af9ea2d0b6f316f9edd4922 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.h
+++ b/content/browser/renderer_host/media/audio_renderer_host.h
@@ -40,6 +40,7 @@
 #include <map>
 
 #include "base/gtest_prod_util.h"
+#include "base/lazy_instance.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process.h"
@@ -61,16 +62,19 @@ namespace content {
 
 class MediaObserver;
 class ResourceContext;
+class WebContentsAudioInputStream;
 
 class CONTENT_EXPORT AudioRendererHost
     : public BrowserMessageFilter,
       public media::AudioOutputController::EventHandler {
  public:
   // Called from UI thread from the owner of this object.
-  AudioRendererHost(media::AudioManager* audio_manager,
+  AudioRendererHost(int render_process_id,
+                    media::AudioManager* audio_manager,
                     MediaObserver* media_observer);
 
   // BrowserMessageFilter implementation.
+  virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
   virtual void OnChannelClosing() OVERRIDE;
   virtual void OnDestruct() const OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message,
@@ -83,6 +87,19 @@ class CONTENT_EXPORT AudioRendererHost
   virtual void OnError(media::AudioOutputController* controller,
                        int error_code) OVERRIDE;
 
+  // Start/stop mirroring all audio output streams associated with
+  // |render_process_id| + |render_view_id| to |destination|.  Any call to
+  // StartMirroring() must be paired with a later call to StopMirroring() since
+  // references are held to both the AudioRendererHost and

[Alpha Left Google, 2012/11/28 20:02:25]

Can we not hold reference to AudioRendererHost?

[miu, 2012/11/28 22:05:50]

Done.

+  // WebContentsAudioInputStream instances while the mirroring session is
+  // active.
+  static void StartMirroring(

[Alpha Left Google, 2012/11/28 20:02:25]

It seems to me these two methods are called on the IO thread, so if you don't do
thread jumping you don't need to hold the reference right?

+      int render_process_id, int render_view_id,
+      const scoped_refptr<WebContentsAudioInputStream>& destination);
+  static void StopMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<WebContentsAudioInputStream>& destination);
+
  private:
   friend class AudioRendererHostTest;
   friend class BrowserThread;
@@ -93,6 +110,9 @@ class CONTENT_EXPORT AudioRendererHost
 
   struct AudioEntry;
   typedef std::map<int, AudioEntry*> AudioEntryMap;
+  typedef std::map<int, scoped_refptr<WebContentsAudioInputStream> >
+      MirrorSessionMap;
+  typedef std::map<int, scoped_refptr<AudioRendererHost> > ActiveHostMap;

[Alpha Left Google, 2012/11/28 20:02:25]

Don't use scoped_refptr, just a * is enough. I suggest you assert that when
AudioRendererHost it is not attached to ActiveHostMap.

[miu, 2012/11/28 22:05:50]

Done.

Not sure what you meant about the asserts.  Are you talking about checking that
AudioRendererHost::FromRenderProcessID() doesn't ever return NULL when called
from StartMirroring() or StopMirroring()?  If so, I don't think asserts would be
appropriate there.  Any races during shutdown are actually completely clean: The
absence of an AudioRendererHost in the ActiveHostMap indicates that there are no
active mirroring sessions on it, which is a reasonabl state to be in.

 
   virtual ~AudioRendererHost();
 
@@ -106,6 +126,10 @@ class CONTENT_EXPORT AudioRendererHost
                       const media::AudioParameters& params,
                       int input_channels);
 
+  // Associate |render_view_id| as the producer of audio for the stream
+  // referenced by |stream_id|.
+  void OnAssociateStreamWithProducer(int stream_id, int render_view_id);
+
   // Play the audio stream referenced by |stream_id|.
   void OnPlayStream(int stream_id);
 
@@ -160,12 +184,35 @@ class CONTENT_EXPORT AudioRendererHost
 
   media::AudioOutputController* LookupControllerByIdForTesting(int stream_id);
 
+  // Global look-up for the AudioRendererHost instance owned by the
+  // RenderProcessHost specified by |render_process_id|.
+  static AudioRendererHost* FromRenderProcessID(int render_process_id);
+
+  // Implementations for StartMirroring() and StopMirroring() that are run on
+  // the IO BrowserThread.
+  static void DoStartMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<WebContentsAudioInputStream>& destination);
+  static void DoStopMirroring(
+      int render_process_id, int render_view_id,
+      const scoped_refptr<WebContentsAudioInputStream>& destination);
+
+  // ID of the RenderProcessHost that owns this instance.
+  const int render_process_id_;
+
   // A map of stream IDs to audio sources.
   AudioEntryMap audio_entries_;
 
+  // A map of render view IDs to the destination for active mirroring sessions.
+  MirrorSessionMap mirror_sessions_;
+
   media::AudioManager* audio_manager_;
   MediaObserver* media_observer_;
 
+  // Global look-up map for currently-active (i.e., IPC channel is open)
+  // AudioRendererHosts.
+  static base::LazyInstance<ActiveHostMap>::Leaky g_host_map_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioRendererHost);
 };